An electrophoretic display panel is known that comprises a plurality of electrophoretic display elements arranged between a first electrode layer and second electrode layer. The display elements are capsules with a dispersion of electrically charged black and white or colored nano-particles in a clear solution. The display panel may be manufactured by depositing an emulsion of these capsules in an appropriate binder as a dense monolayer onto an organic substrate with an electrode of an electrically conductive, transparent material, such as indium tin oxide (ITO). After that, the binder is cured to make the system mechanically robust. The electrophoretic medium so obtained is laminated by a thin adhesive layer onto a backplane, thereby sandwiching the capsules, binder and adhesive between the ITO electrode and the backplane electrodes (e.g. pixel pads of an active-matrix display). The black and white particles are moved within the capsules by applying an electric field between the ITO and backplane electrode, thereby enabling rendering of grey levels.
The behavior of the display panel is influenced by its temperature in several ways. The viscosity of the capsule fluid, and therewith the mobility of the nano-particles, is dependent on the temperature. In addition, if the display elements are arranged as an active matrix, the behavior of the transistor elements of the active matrix is dependent on temperature. Last but not least, the electric behavior (mainly resistance, further denoted herein as cell gap resistance or briefly CGR) of the binder, capsule walls and adhesive layer will change dramatically with changing temperature. Generally these effects will cause the switching speed to increase with increasing temperature. Care has to be taken however that the decreasing resistance between the ITO and the backplane electrode does not cause the switching behavior to degenerate. This will cause sub-optimal driving and thereby visible artifacts such as ghosting, image sticking or deviations in grey scale rendering. In particular a rollable display in its rolled out state adapts very fast to the temperature in the environment as it is extremely thin and lightweight.
Accordingly it is necessary to drive the display elements of the display panel with a temperature dependent driving scheme to achieve an optimal switching behavior across the complete operational temperature range.
US2007/0052665 A1 describes an electrophoretic display unit that is provided with an embedded temperature sensor embedded in the display panel, typically a silicon based sensor. The sensor or other temperature sensing device equipped with a transducer transmits a digital control signal to a processor. The processor uses this digital control signal to drive the display elements with a progressive number of pre-pulses at higher temperatures.